Chapter 14 - Energy Generation in Mitochondria and Chloroplasts Flashcards
Which activated carrier contains a high-energy bond whose hydrolysis releases a large amount of free energy?
- ATP
- water
- NADH
- glucose
- high-energy electrons
ATP
(The energy released by the hydrolysis of ATP to ADP can be harnessed to drive many otherwise energetically unfavorable chemical reactions in cells.)
Which of these processes require a membrane?
- generation of energy by mitochondria
- generation of ATP by photosynthesis in bacteria
- generation of ATP by photosynthesis in plants
- generation of ATP by oxidative phosphorylation
- generation of ATP by glycolysis
- generation of energy by mitochondria
- generation of ATP by photosynthesis in bacteria
- generation of ATP by photosynthesis in plants
- generation of ATP by oxidative phosphorylation
(The generation of ATP by oxidative phosphorylation differs from the way ATP is produced during glycolysis in that it requires a membrane-bound compartment, such as mitochondria. A related membrane-based process produces ATP during photosynthesis in plants and photosynthetic bacteria.)
What is true of the organelles that produce ATP in eukaryotic animal cells?
- They evolved from bacteria engulfed by ancestral cells billions of years ago.
- They harbor eukaryotic-like biosynthetic machinery for making RNA and protein.
- They contain the same genes as the chloroplasts of plant cells.
- They have a separate set of DNA that contains many of the same genes found in the nucleus.
- They reproduce sexually.
They evolved from bacteria engulfed by ancestral cells billions of years ago.
(Mitochondria reproduce in a manner similar to most prokaryotes, harbor bacterial-like biosynthetic machinery for making RNA and proteins, and retain their own genomes. Such facts are considered evidence of their bacterial ancestry.)
True or False:
The presence of DNA, as well as bacteria-like machinery for making RNA and proteins, is evidence of the prokaryotic ancestry of these organelles.
True
Which part of the mitochondrion contains the proteins that carry out oxidative phosphorylation?
The inner mitochondrial membrane
(The inner mitochondrial membrane, which is folded into cristae, contains the proteins that carry out oxidative phosphorylation, including the electron-transport chain and the ATP synthase that makes ATP.)
Which activated carriers are produced by the citric acid cycle?
- NADH
- FADH2
- NADPH
- ATP
- GTP
- CO2
NADH
FADH2
GTP
(NADH and FADH2 donate their high-energy electrons to the electron-transport chain in the inner mitochondrial membrane. The citric acid cycle also produces GTP, an activated nucleoside triphosphate closely related to ATP.)
The movement of electrons through the electron-transport chain in mitochondria does which of the following?
- produces oxygen
- produces NADH
- pumps ATP across the inner mitochondrial membrane
- pumps protons out of the mitochondrial matrix
- consumes ATP
pumps protons out of the mitochondrial matrix
(Protons are pumped across the inner mitochondrial membrane and out of the mitochondrial matrix against their electrochemical gradient. This stores energy in an electrochemical gradient that can be used by ATP synthase to power the production of ATP.)
When protons move down their electrochemical gradient into the mitochondrial matrix, what do they do?
- produce NAD+
- move electrons through the respiratory chain
- produce NADH
- consume ATP
- produce ATP
Produce ATP
(The passage of protons down their electrochemical gradient through ATP synthase causes the enzyme to produce ATP from ADP and Pi.)
Which of the following statements are true of electron transfer in the electron-transport chain?
- NADH has a relatively high electron affinity and initiates the electron-transport process.
- Electrons move toward molecules with a high redox potential.
- NADH is a strong electron donor.
- Each electron transfer is an oxidation–reduction reaction.
- When an electron carrier accepts an electron, it becomes oxidized.
- Electrons move toward molecules with a high redox potential.
- NADH is a strong electron donor.
- Each electron transfer is an oxidation–reduction reaction.
(All electron transfers represent redox reactions. NADH is a strong donor of electrons, and electrons move toward molecules with a high redox potential, which translates into a high affinity for electrons.)
During electron transport, which serves as a ready source for protons that can be pumped across the membrane?
- ATP
- glucose
- H2O
- NADH
- O2
H2O
The protons in water are highly mobile, and they are able to move rapidly from one water molecule to another.
When the difference in redox potential between two molecules is highly positive, what is true of the transfer of electrons between them?
- It is accompanied by a rise in ΔG.
- It produces ATP.
- It is highly favorable.
- It requires an input of energy.
- It is highly unfavorable.
It is highly favorable.
(A highly positive difference in redox potential translates into a large negative free-energy change (ΔGo) for the transfer of electrons—a reaction that is thus highly favorable.)
Most of the energy for the synthesis of ATP comes from which molecule?
- NADH produced by glycolysis
- NADH produced by the citric acid cycle
- FADH2 produced by the citric acid cycle
- NADH produced by the conversion of pyruvate to acetyl CoA
- GTP produced by the citric acid cycle
NADH produced by the citric acid cycle
(One turn of the citric acid cycle produces three molecules of NADH. Because glycolysis produces two molecules of pyruvate, six NADHs will be produced per molecule of glucose oxidized.)
Stage 1 of photosynthesis is, in large part, equivalent to what process?
- glycolysis
- the production of acetyl CoA by the pyruvate dehydrogenase complex
- oxidative phosphorylation
- the citric acid cycle
- the carbon-fixation cycle
Oxidative phosphorylation
(In this stage of photosynthesis, the movement of electrons along an electron-transport chain is used to generate a proton gradient that can be used by ATP synthase to produce ATP. The same mechanism occurs during oxidative phosphorylation.)
When an electron is removed from the reaction center of photosystem II, the missing electron is replaced by an electron from which of the following?
- H2O
- H+
- photosystem I
- sunlight
- manganese
H2O
Photosystem II includes a water-splitting enzyme that extracts electrons from water, producing O2 as a by-product.
In this simplified diagram of the reactions of the carbon-fixation cycle, which step is catalyzed by the enzyme Rubisco?
- A
- B
- C
- D
- E
E
(In the first reaction of the carbon-fixation cycle, here labeled step E, Rubisco catalyzes the addition of CO2 to a five-carbon molecule of ribulose 1,5-bisphosphate to produce two three-carbon molecules.)
What is true of stage 2 of photosynthesis?
- It takes place in the chloroplast grana.
- It generates a proton gradient across the thylakoid membrane.
- It produces all of the O2 we breathe.
- It begins with the production of ATP and NADPH and ends with their consumption.
- It produces glyceraldehyde 3-phosphate in the stroma.
It produces glyceraldehyde 3-phosphate in the stroma.
(In stage 2 of photosynthesis, which begins in the stroma, the ATP and the NADPH produced in stage 1 are used to drive the manufacture of glyceraldehyde 3-phosphate from CO2.)
What is one reason that plants do not generally produce sugars after dark?
- O2 is unavailable after dark.
- The enzymes involved in stage 2 of photosynthesis are inactivated in the dark.
- The enzymes involved in stage 1 of photosynthesis are inactivated in the dark.
- CO2 is unavailable after dark.
- The enzymes involved in stage 2 of photosynthesis are inactivated in the light.
The enzymes involved in stage 2 of photosynthesis are inactivated in the dark.
(In addition to requiring the ATP and NADPH produced by the light-dependent reactions in stage 1 of photosynthesis, several of the enzymes required for carbon fixation are inactivated in the dark and reactivated by light-stimulated electron transport.)
The first living cells on Earth—whether prokaryotes or primitive eukaryotes—most likely generated ATP by what process?
- aerobic cell respiration
- fermentation
- oxidative phosphorylation
- photosynthesis
- nitrogen fixation
Fermentation
(In fermentation, organic molecules are broken down to generate energy without the involvement of oxygen. Such processes likely provided energy for the earliest cells on the planet.)
During Earth’s history, with the rise of cyanobacteria, what molecule began accumulating in the atmosphere for the first time?
- CO2
- H2O
- O2
- N2
O2
(The availability of O2 made possible the evolution of nonphotosynthetic organisms that used aerobic metabolism to make their ATP.)
What is true of the evolution of electron transport systems?
- They are a relatively recent evolutionary innovation.
- They are evolutionarily ancient and likely provided energy for the earliest cells on Earth.
- In ancient prokaryotes, they did not require the use of a membrane.
- Their requirement for oxygen as an electron acceptor means they evolved first in photosynthetic prokaryotes.
- The earliest ones involved using H2O as an electron donor.
They are evolutionarily ancient and likely provided energy for the earliest cells on Earth.
(Membrane-based mechanisms for the generation of energy appeared very early in the history of life, more than 3 billion years ago.)
Antibiotics should inhibit bacterial cell growth without generating side effects in the human patient, but that is not always the case. Some antibiotics that inhibit bacterial protein synthesis by binding to bacterial ribosomes induce negative side effects in patients. What is the most likely cause of these side effects?
- The antibiotics interfere with chloroplast ribosomes.
- The antibiotics interfere with cytoplasmic ribosomes.
- The antibiotics interfere with ribosomes attached to the ER, impairing RER function.
- The antibiotics interfere with mitochondrial ribosomes.
The antibiotics interfere with mitochondrial ribosomes.
(Mitochondria are of bacterial origin and contain ribosomes more similar to bacterial ribosomes than the ribosomes found in the eukaryotic cell cytoplasm. Antibiotics that target bacterial cell wall synthesis do not induce mitochondrial side effects.)
To explore how yeast cells metabolize glucose, investigators use a DNA microarray to examine the effect the sugar has on the expression of a variety of genes. Cultured yeast cells are supplemented with high concentrations of glucose. mRNAs are extracted from the cells, converted into cDNAs, and labeled with a fluorescent marker. The samples are then hybridized to a DNA microarray that includes probes representing yeast genes.
Shown here is a data set representing genes involved in ribosome biogenesis and electron transport. Red indicates that supplementing the growth medium with glucose has increased the expression of the genes, whereas green indicates that the added glucose has decreased gene expression.
Based on this data, what can be concluded about how yeast cells behave when grown in the presence of high concentrations of glucose?
- Yeast cells shut down protein synthesis when grown in the presence of high concentrations of glucose.
- Yeast cells exposed to high concentrations of glucose grow by fermentation.
- Yeast cells grow poorly in high concentrations of glucose.
- Yeast cells consume large amount of oxygen as they break down glucose.
- Yeast cells are able to extract the maximum amount of energy from glucose via oxidative phosphorylation.
Yeast cells exposed to high concentrations of glucose grow by fermentation.
(Yeast cells grown in the presence of high glucose concentrations decrease the expression of genes that encode components of the electron-transport chain. This suggests that, under these conditions, the cells are not relying heavily on oxidative phosphorylation to break down glucose and generate ATP.)
Protons are pumped across the mitochondrial inner membrane as electrons are transferred through the mitochondrial electron transport chain. Which of the following statements about proton pumping are correct?
Choose one or more:
- The NADH dehydrogenase, cytochrome b-c1, and cytochrome oxidase complexes all pump protons across the membrane.
- The mitochondria use the proton gradient to synthesize ATP.
- Protons are pumped into the matrix of the mitochondria.
- The pH inside the mitochondrial matrix is higher than in the intermembrane space.
- The NADH dehydrogenase, cytochrome b-c1, and cytochrome oxidase complexes all pump protons across the membrane.
- The mitochondria use the proton gradient to synthesize ATP.
- The pH inside the mitochondrial matrix is higher than in the intermembrane space.
(The NADH dehydrogenase, cytochrome b-c1, and cytochrome oxidase complexes all pump protons from the matrix to the intermembrane space, which results in a higher pH inside the matrix. The mitochondria then use the energy of the proton gradient to synthesize ATP.)
Antimycin A is a piscicide (fish poison) used to manage fisheries and kill invasive species. Antimycin A blocks the transfer of electrons through the cytochrome b-c1 complex. What components of the electron transport chain are bound to high-energy electrons after treating a mitochondrion with antimycin A?
- All three complexes and NADH are bound to high-energy electrons.
- None of the complexes are bound to high-energy electrons.
- O2 and the cytochrome c oxidase complex are bound to high-energy electrons while NADH and the NADH dehydrogenase complex are not.
- NADH and the NADH dehydrogenase complex are bound to high-energy electrons while O2 and the cytochrome c oxidase complex are not.
NADH and the NADH dehydrogenase complex are bound to high-energy electrons while O2 and the cytochrome c oxidase complex are not.
(The molecules before the blockage will still bind high-energy electrons after electron transfer. No transfer of high-energy electrons will occur to molecules that come after the blockage and these molecules will not be bound to high-energy electrons.)
